Strange other world

A cell is not just a bag of juice. It is packed with solid structures, mazes of intricately folded membranes. There are about 100 million million cells in a human body, and the total area of membranous structure inside one of us works out at more than 200 acres. That's a respectable farm.

What are all these membranes doing? They seem to stuff the cell as wadding, but that isn't all they do. Much of the folded acreage is given over to chemical production lines, with moving conveyor belts, hundreds of stages in cascade, each leading to the next in precisely crafted sequences, the whole driven by fast-turning chemical cogwheels. The Krebs cycle, the 9-toothed cogwheel that is largely responsible for making energy available to us, turns over at up to 100 revolutions per second, duplicated thousands of times in every cell. Chemical cogwheels of this particular marque are housed inside mitochondria, tiny bodies that reproduce independently inside our cells like bacteria. As we shall see, it is now widely accepted that the mitochondria, along with other vitally necessary structures within cells, not only resemble bacteria but are directly descended from ancestral bacteria who, a billion years ago, gave up their freedom. Each one of us is a city of cells, and each cell a town of bacteria. You are a gigantic megalopolis of bacteria.